Large Girth And High Rate Low-Density Parity-Check Codes Constructing For High-Speed Optical Communications

Low-Density Parity-Check(LDPC) codes are a class of capacity approaching error-correcting codes and a good liner block codes, which perform at a rate extremely close to Shannon capacity. Its error-correcting ability has tight connection with the construction way in encoder. QC-LDPC codes are characterized by the parity-check matrix which consists of small square blocks which are the zero matrix or circulate permutation matrices. It is an important branch of LDPC codes. Encoding of a quasi-cyclic(QC) LDPC code Can be achieved with simple shift-registers, being prone to hardware realization.In recent years, LDPC codes are using in the fields of mobile communication, satellite communications and magnetic storage system because of its excellent performance. It can improve the optical communication system transmission performance if the system using LDPC codes as FEC (Forward Error Correction) Code. However, we should consider the fiber communication system’s character, eg. high rate and high efficiency.We first codec process simulation and analysis of different factors such as channel model, decoding algorithm, girth size of the decoding performance.We propose to construct a QC-LDPC code method with large girth and high bit-rate.Finally, for high-speed fiber-optic communication systems, simulation, the channel model, has been its probability density function. And check QC-LDPC codes in which the performance, selected for transmission based QC-LDPC codes.